For cosmetic purposes, contact lenses having one or more colorants dispersed in the lens or printed on the lens are in high demand. These colored contact lenses enhance the natural beauty of the eye, or provide unique patterns on the iris of the wearer, or provide non cosmetic patterns or marks, such as rotation marks, inversion marks, product/brand codes, lot numbers, “DEMO” lenses, and the like, which are of benefits to wearers, eye-care practitioners and manufacturers.
Presently, methods of printing inks onto contact lenses involve clichéink transfer printing. A typical example of this printing follows. An image is etched into metal to form a cliché. The cliché is placed in a printer. Once in the printer, the cliché is inked by either an open inkwell doctoring system or by a closed ink cup sliding across the image. Then, a silicone pad picks up the inked image from the cliché and transfers the image to the contact lens. The silicone pads are made of a material comprising silicon that can vary in elasticity. The properties of the silicone material permit the inks to stick to the pad temporarily and fully release from the pad when it contacts the contact lens.
There are several disadvantages associated with using cliché ink transfer printing to color contact lenses. This method lacks consistency. Slight differences in the silicone pad can cause wide variation in image quality, effecting dot resolution and color reproducibility. Further, multiple color layering is difficult and time consuming. Further still, the design and printing process using this method is slow. After an image is fully designed, it can take about two weeks before that image is etched onto a cliché. The set-up is painstakingly detailed and lengthy when more than one color is going to be printed on the lens using this method. The difficulty and slowness of this printing method inhibits business strategies, making it difficult to offer consumers a chance to design and print their own contact lenses at the point of purchase.
Ink-jet printing method may be used to replace the above-mentioned methods for printing colored images with high quality on a contact lens. However, current ink-jet printing technologies and systems are designed to print colored images on a flat object such as papers by moving an ink jet head (or a part) in a simple x-y-z translation (Cartesian) motion. These systems and methods in the prior art are not suitable for printing colored images with high quality on objects with curved surfaces to be printed, such as hemispherical contact lenses or molds for making contact lenses, especially in an industrial setting for high-throughput production of colored contact lenses. Therefore, there are needs for ink-jet printing methods and systems capable of printing colored images on curved articles. There are also needs for printing methods and systems that can be used in the high-throughput production of colored contact lenses.